Am. J. Respir. Crit. Care Med.,
Volume 162, Number 5, November 2000, 1668-1673
Pulmonary Capillary Blood Volume in
Hyperpnea-induced Bronchospasm
DAVID A.
KAMINSKY
and
MARY
LYNN
Division of Pulmonary Disease and Critical Care Medicine, Department of Medicine, University of Vermont College of Medicine,
Burlington, Vermont
Reactive hyperemia of the bronchial circulation has been postulated to contribute to the airway narrowing that occurs following exercise or hyperpnea in subjects with asthma with hyperpnea-induced bronchospasm (HIB). Changes in lung parenchymal mechanics also occur in HIB, including increases in peripheral airway
resistance. Since the peripheral airways and lung parenchyma are
supplied by the pulmonary circulation, and changes in the pulmonary circulation could alter airway resistance or tissue mechanics,
we hypothesized that pulmonary capillary blood flow would increase in association with HIB, resulting in increases in pulmonary
capillary blood volume (VC). We measured VC by using two test
gases of varying oxygen concentration to determine the diffusing
capacity of the lung for carbon monoxide (DLCO) before and after
a period of hyperpnea in 13 subjects with asthma with HIB and 10 control subjects without asthma. Despite subjects with asthma
having a significant fall in FEV1 following hyperpnea compared
with control subjects (
FEV1 = 
26 ± 12 versus 4 ± 4%, mean ± SD, p < 0.001), there was no change in the DLCO or VC from baseline values. We conclude that pulmonary capillary blood volume
does not change following hyperpnea, and therefore that changes
in pulmonary blood flow are not associated with HIB.
